Telephone system



Aug. 3 1926.

G. BABCOCK TELEPHONE SYSTEM Filed Jufie 11, 1921 2 Sheets-Sheet 1 Aug.3, 1926. v 1,594,587

G. BABCOCK TELEPHONE SYSTEM Filed June 11, 1921 2 Sheets-Sheet 2Patented Aug. 3, 1926.

UNITED STATES PATENT OFFICE.

TELEPHONE SYSTEM.

Application filed June 11, 1921.

My invention relates to telephone systems, and more particularly relatesto systems in which the service to the subscribers is metered throughthe use of reverse ourrent flow over the calling line. The presentapplication is specifically concerned with novel means for securing thereversals of current, and for applying them to the calling line. Thecurrent reversing device, which is the subject of certain of the claimshereafter, is not limited to the employment in a telephone system, or,if employed in a telephone system, is not limited to the specific methodof connection and application which I have specifically described in thefollowing specification.

In carrying out the matter of metering a telephone service, I havedevised a system of current reversal operating on meters installed onthe subscribers premises I have developed a number of different methodsand suitable means for securing the reversal of polarity upon thecalling line, all of which have proven satisfactory, but of a generallymore expensive construction than I find possible according to thepresent invention.

The primary aim of the present invention is to provide. a simple,positive and inexpensivemeans for securing reversals of current flowsuitable for actuating tclechronometers on telephone lines, and thelike. For this purpose, it is necessary that the .change in potentialover the telephone line he made quickly and positively, without anychange or sharp interruption of current flow, which would be exceedinglydisagreeable and highly objectionable in a telephone system. Accordingto the present invention, I provide a resistance, or pair ofresistances, for each direction of current flow, these resistances, orpairs of resistances, being connected to the answering end of the cordcircuit constantly, through a potentiometer or \Vheatstone bridgeconnection, so that, by reducing a resistance, or pair of resistances,the polarity of the terminals of the pole-changing device will bereversed.

The opposite resistances in the Threatstone bridge are arrangedmechanically side by side, and mechanically such opposite pairs ofresistances are compressed and released alternately, so that thepotential of the terminals is shifted quickly and Serial No. 476,713.

smoothly from one time to another, thereby causing reversal of current.

. In order to teach those skilled in the art in the manner ofconstructing and racticing my invention, I shall now descri e anembodiment of the same, as illustrated in the accompanying drawings.

In the drawings:

Figure 1 is a diagrammatic lay-out of a telephone system embodying myinvention;

Figures 2 and 3 illustrate the development of the basic idea involved inmy pole-changmg device;

Figure 4 is a" fragmentary diagrammatic 1loaylout of the pole changer orWheatstone Figure 5 is a side elevational View, partly diagrammatic, ofthe mechanical linkage for operating the compression rheostat;

Figure 6 is a plan View, partly in section, showlng a modified form ofthe same; and

Figure 7 is a fragmentary illustration of a polarized relay which isemployed to control the actuation of the compression rheostat.

In the system employing my invention, I dispose at the subscribersstations A and B, in conjunction with the usual telephone apparatus, acall registering device 1 adapted to be operated by reversals ofcurrent. The particular meter which I prefer to employ is described inmy copending application, Serial No. 476,712, filed June 11, 1921. Thismeter is characterized by the use of two series coils connected in thetwo sides of the talking line, and provided with suitable polarizingmeans and counter-actuating mechanism, whereby a complete cycle of thereversal of current is required for the actuation of the startingmechanism.

Any other suitable metering device operating upon reversal of currentmay be employed, as the present application relates more particularly tothe manner of and means of securing current reversal.

The calling station A comprises the usual transmitter 2, receiver 3,induction coil 4,

hook switch 5, and ringer or call hell 6. The

station is connected to suitable terminals at central over the linewires 7 and 8, which line wires are provided with connections to thecentral battery 10, for supplying normal polaritof current over theline. The line is provided at central with a suitable answering plug 17for cooperating with thehline and multiple jacks, 1n makingconnectionsand inter-connections. The answering plug 16 is connected to the talkingstrrands 18 and 19, and is provided with a third conductor 20 forcontrolling the actuation of the cut olf relay 13, and the sleeve relay21. A listening key 22 for placing the operators talking set 24 incommunication with the strands 18 and 19 is also provided. At theringing end of the cord circuit, the plug 17 is connected to the talkingstrands 25 and 26, and is also connected tothe third conductor 27, whichserves to energize the line out off relay 13' of the called line 7' 8and the sleeve relay 27 The operator is provided with a ringing key 28,which 15 adapted to connect the ringing generator 29,

or other source of ringing current, to the conductors of the calledline.

While I have illustrated a three strand cord circuit in the particularembodiment which I have elected todescribe, it is to be understood thatthe invention is not limited in any manner to the em loyment of athree-' strand cord circuit, an myillustration of the same is for thepurpose of clearly il'-' lustrating my invention in as simple a manneras possible.

The answering end of the cord circuit is" supplied with battery from thecentral source 10 over suitable connections which will be describedlater, and which include the answering supervisory relay 30, which, inconnection with the sleeve relay 2], controls the supervisory signal 31.In a similar manner, battery is fed to the ringing end of the cordcircuit from the central battery over suitable connections, in thiscase-wires 32, winding 33, and conductor 35, to the tip strand 25, andfrom ground or negative side of the battery, over the winding 36 of thesuperiisory relay 34, conductor 37, to the ring or sleeve strand 26 ofthe ringing end of the cord circuit. The potential upon the ringing endof the cord circuit always remains in the same direction, due to theconnections above described, so that no reversals of current upon thecalled line occurs, the calling line only being charged for the call.

The pole changing device 38 comprises two gtirs of compressionresistances, R R and 2 R, between which battery is connected over theconductors 39 and 40, and between which pairs is an actuating memher inthis case a bar 41, connected to a suitable armature for the operatingmagnets 42 and 43. The circuits for the actuating magnets 42 and 43 arecontrolled by the polar.- ized relay 44, and the time controlled-relay45. The relay 45 is in turn governed by the time controlled circuitbreaker and maker 46, which includes the cam wheel 47 and the contacts48 for periodically closing a circuit over the wire 49 for the windingof the controlling relay 45. The controlling relay 45 has a pair ofcontacts 50, which close a circuit from battery over the wire 51 to theterminals of the two actuating magnets 42 and 43, the other terminals ofwhich magnets are connected respectively to contacts 52 and 53 of thepolarized relay 44. A movable armature contact 54 is connected toground, and depending upon the polarity prevailing upon the terminalwires'56 and 57 of the pole changing device 38, the armature 54 willclose contact with the corresponding one of the contacts 52, 53. Thepolarized relay 44 has a Winding 58, which is bridged across theterminals 56 and 57 by means of wires 60 and 61. The polarized relay 44is thus subjected to the'same polarity as that existing upon the callingline, and the shifting of the polarity upon the calling line controlsthe circuit of the actuating relays 42 or 43.-

In order to make more clear the operation of the pole changer, I haveshown diagrammatically in Figure 4, a detached and simplified diagram ofthe connections showingthe relations of the resistances in the circuit.The battery 10 is connected to the .common terminal 62 of theresistances R and R and the common terminal 63 of the resistances R andR The terminals 56 and V57,o f the pole-changer, which lead to thetalking strands 18 and 19, respectively, through the supervisory relay30, are connected to the common points 64 and 65, respectively, thesepoints being the connecting points of the resistances R and R and R andB, respectively. The resistances R and R are mechanically compressedtogether, these resistances comprising carbon piles, and the resistancesR and R are actuated simultaneously, these resistances also comprisingcarbon piles. It can now be seen that if the resistances R R R and R areall equal, no difference of potential of the terminals 56 and 57 willexist. v It, now, the resistances R and R are simultaneously compressedto reduce the value of the same, the terminal 56 will exhibit a strongnegative potential, and the terminal 57 will exhibit a strong positivepotential, as indicated in Figure 3. It, now, the pressure onresistances R, R is relaxed. and simultaneously the pressure ofresistances R R" is increased, the terminal 56 will exhibit a positivepotential, and the terminal 57 a tances are connected in series with thebat-.

tery 10. The other terminal 56 of the circuit is connected between theresistances R and R Assuming that the resistances It and R are of avariable type, such as carbon piles, or of any other suitable character,so that they may be gradually increased or decreased, and assuming thatone of the resistances is increased while the other is decreased, itwill be seen at once that by a shifting of the value of the resistancein said circuit, the normally equipotential points to which theterminals 56 and 57 are connected will change.

It is to be noted that in this potentiometer circuit, the maximumvoltage which can be secured is only half of that of the battery, and ifsuch a system were employed the difiiculty of maintaining proper batteryconnections and proper voltages upon the lines and relays would bepronounced.

I have conceived, therefore, that this difficulty might be remedied byemploying two potentiometer circuits connected together, whereupon thefull voltage of the battery might be employed upon the terminals, and Ihave therefore shown in Figure 3 the transitional stage between theconception of Figure 2 and the conception of Figure 4. In thisconstruction I employ two separate batterics, 10 and 10 in separatepotentiometer circuits, S6 and 86", respectively, and connect thesebatteries together at their neutral points; whereupon, I am able to takethe full potential of the battery from the terminals 56" and 57". Thepotentiometer circuit 86 contains resistances R and R while thepotentiometer circuit 86" includes the resistances t and R. Since thetwo battcrics are connected in the same direction, perform the samefunction, and the added voltage of two halves is always provided, it ispossible to dispense with one of the batteries, wereupon the circuitassumes the form shown in Figure 4, namely, a \Vlueatstone bridge havingsubstantially equal resistances in all four of the arms. It is perhapsinadequate to state that the resistances of all four arms is equal,since the desired construction is that the resistances will havesubstantially. the same characteristics through the various stages ofcompression or release which they must oc cupy. It is not essential thatthese resistances be absolutely balanced at all times, but a conditionof balance is desirable. The Wheatstone bridge is in reality a doublepotentiometer circuit.

I consider that this constitutes a novel process of producing a reversalof 'potential upon a telephone circuit, and am claiming the sameaccordingly.

The particular means by which I accomplish the reversal mechanically isillustrated in Figure 5, and a modification thereof illustrated inFigure 6.

In Figure 5 I provide a walking beam (36, each arm thereof havingconnected thereto a solenoid plunger 67, 68, the co-operating solenoids69 and 70 corresponding to the actuating magnets 42 and 43 ofFigure 1.Each arm of the walking beam 66 is connected pivotally, as at 71 and 72,to a co-operating link or strut 73, 74 respectively, for creating apowerful thrust upon the compressible resistances R R These resistancespreferably comprise sleeves of insulation containing carbon granules, orother compressible resistance material, such as discs or wafers ofcarbon, or the like. As shown in Figure 5, the thrust rods 73 and 74operate through levers 75 and 76, instead of'bearing directly upon theends of the resistances R R These levers 75 and 76 are pivoted at theircentral portions, as shown at 77 and 78, and serve merely to form a morecompact arrangement of the device. It will be seen at once that thewalking beam 66, in connection with the thrust. rods 73 and 74, form apair of toggle arms of relatively great power for imposing suitablepressure upon the carbon piles R R I wish to call attention, in thisconnection, to the fact that the final movement of the toggle mechanismis particularly powerful, both because of the increased power of thetoggle as the same approaches a straight line, and also because of theincreased power of the solenoid, or other electromagnet, when attractingits coreor armature 67' 68. Any

ltltl llO desired characteristic may be obtained by suitably designingthe ratio of the toggle and the characteristic of the operating magnetor solenoid. In addition, the pressure will remain upon the piles untilthe toggle is broken.

In Figure 6 I have shown a modified form of pole changer, in which Iemploy a straight actuating bar 41, which serves as an armature for thetwo operating magnets 42 and 43; in this case, the magnets are of theshell type, in which the magnetic circuit is closed through an outermagnetic shell 79, and through the magnetic bar 41, so that the powerfulpull upon the said armature 41 is secured when the winding of thecorresponding magnet is energized. The

armature'41 is insulated from electrical contact with the resistances bybuttons of insulating material as indicated at 80.

In Figure 7 I have illustrated the manner in which I construct theterminals of the polarized relay 44. The contacts are made by theemployment of small rollers of nonarcing material pivoted upon the endsof suitable springs, these rollers adapted when brought into contact toroll slightly, and thus constantly change the point of contact betweenthem, thereby greatly prolonging the life of the same.

I shall now describe briefly the operation of a system embodying theinvention. Assuming that the party at the sub-station A desires to beconnected to the party at the sub-station B: The receiver 3 is raised,placing the transmitter and receiver in circuit, and operating the linesignal 14 to call attention to the fact that the party at the station Adesires to make a call. The operator makes connection with the answeringplug 16 replacing the line signal and connecting the strands 18 and 19to the line wires 7 and 8. At the sametiine, current of the prevailingpolarity flows out over the talking strands 18 and 19, and over the linewires 7 and 8, and supplies talking current to the instruments at thesubstation A. The operator, through the medium of the listening key 22,receives the order for connection from the party at the sub-station A,and assuming that the line connecting with the station B is desired, theoperator presses the terminals of said line and proceeds to make theconnection. The ringing key 28 is actuated to project the ringingcurrent over the called line, and when the party at the sub-station Banswers, current flows in-normal direction over the line of the calledparty, and conversation between the parties may be carried on.

The operation of the pole changer continues at all times, and in thesystem I have illustrated th calling party is charged for all of thetime consumed in making a connection and consummating the conversation.If desired, the calling party may be charged for only the time duringwhich connection between the two parties is established .by cutting theterminals of the relay 30 through the contacts of the supervisory relay34, so that until the calling party responds, normal polarity of currentprevails upon the calling line. Since both methods of operation areknown, I do not consider it necessary to illustrate the same in detail.

The operation of the pole changer is as follows: The time controlled cam47 rotates continuously, intermittently making contact at the contacts48 to close the circuit of the relay 45 over the Wire 49. The closing ofthe contact 48 is only momentary,

magnet 43, wire 84, contacts 53, to ground.

Thereupon, the resistances R and R are compressed, and the pressur onresistances R and R relieved, reversing polarity upon the terminals 56,57, and causing the armature 54 of the polarized rcla 44 to swing to thealternate contact 52. efore the armature 54 arrives at the contact 52,the cir-' cuit at the contact 50 is opened until the time wheel 47 againcloses the contact 48 to energize the relay 45.

If desired, a locking circuit for the relay 45 may be closed when thecontacts 50 are closed, this locking circuit being opened by the throwof the armature 54 upon the contact on which it previously rested. I

A changeof polarity occurring on the calling line from positive tonegative, and back to positive, or vice versa, causes an actuation orregistration .upon the meter 1 at the calling station. If desired, themeter may be actuated by a reversal of current only, that is, frompositive to negative, or vice versa, but I prefer the use of a meterwhich requires a complete cycle of alternation for registration of acount thereupon.

1 do not intend to be limited to the details of construction shown ordescribed.

I claim:

1. In combination, a telephone line, a closed battery circuit includingtwo substantially similar variable resistances across whichsubstantially the full voltage oi the battery is impressed, a firstconnection from one side of said line to said circuit at a point betweensaid resistances, and a second connection from the other side of thetelephone lineto said circuit, said second connection being made at a.point normally equi-potential with the first point, and means forautomatically increasing the resistances.

2. In combination, a tele )hone line, a closed battery circuit includingtwo substantially similar variable resistances across whichsubstantially the full voltage of the battery is impressed. a firstconnection from one side of said line to said circuit at a point betweensaid resistances, and a second connection from the other side of saidline to said circuit, said second connection being made at a pointnormally equi-potential with the first point, and means forsimultaneously incrcasing one resistance while reducing the other, andvice versa.

3. In combination, a. telephone line, a

closed circuit having a source of current and including twosubstantially similar variable resistances across which substantiallythe full voltage of the source is impressed, said resistances comprisingcarbon piles, a first connection from one side of said line 'to saidcircuit at a point between said resistances, and a second connectionfrom the other side of said line to said circuit, said second connectionbeing made at a point normally equi-potential with the first point, andmeans for increasing the pressure on one carbon pile while reducing thepressure on the other carbon pile.

4. In combination, a telephone line, a closed circuit having a source ofcurrent and including two substantially similar variable resistancesacross which substantially the full voltage of the source is impressed,a first connection from one side of said line to said circuit at a pointbetween said r'e-- actuating magnet for increasing one resis-v tancewith respect to the other, and vice versa. 7

5. In combination, a telephone line having a call meter adapted to beoperated by reversals of current, means for supplying current to themeter, said means comprising a cord circuit having a pole changingdevice for supplying current to the talking strands of the cord circuit,said pole changing device comprising a pair of carbon piles adapted tobe periodically compressed alternately.-

6. In combination, a telephone line having a meter adapted to beoperated by current reversals, a switching circuit at central connectedto means for supply talking current to the line and to the meter, saidmeans comprising a potentiometer circuit containing two variableresistances, and means for periodically and alternately varying saidresistances, said means being adapted to vary said resistances smoothly,whereby no sharp change of potential is created on the talking circuit.

In combination, a telephone line, a potentiometer circuit comprising twovariable compressible resistances, terminals leading to said telephoneline connected to said'potentiometer circuits, electromagnetic means forvarying said resistances alternately, and time controlled meansgoverning the actuation of said electromagnetic means.

-8. In a telephone system, a talking line, means for supplying currentperiodically in reverse direction over said line, said means comprisinga potentiometer circuit including a pair of non-interruptible variableresistances, a pair of electro-magnets for alter-.

nately varylng said resistances, a time controlled circuitco-ntr'ollerfor periodically actuating one of said electromagnets, and a polarizedcircuit changer for determining the electromagnets to be actuated.

9. In combination, a telephone line having a call meter adapted to beactuated by reversals of current, polarity means for supplyingperiodically reversed current over said line, said means comprising alink circuit having a pole changing device for sup-' plying current tothe talking strands of the link circuit, said pole changing devicecomprising a pair of carbon piles adapted to be periodically compressedand released alternately, and means for periodically compressing andreleasing said piles.

10. In combination, a telephone line having a meter actuated byvariations of current, a potentiometer circuit for supplying talkingcurrent to the line, said circuit comprising a pair of compressiblevariable re-' sistances and means for alternately compressing saidresistances.

In witness whereof, I hereunto subscribe my name, this 2nd day of JuneA. D., 1921.

GARRISON BABOOCK.

